Subj : Wx Terms (E)(2)
To   : All
From : Daryl Stout
Date : Mon Nov 06 2017 09:43 am

ENDG
Ending

Energy Dissipator
In hydrologic terms, a structure which slows fast-moving spillway flows in
order to prevent erosion of the stream channel.

Energy Helicity Index
An index that incorporates vertical shear and instability, designed for
the purpose of forecasting supercell thunderstorms.

Engineer's Level
A telescope which is attached to a spirit-tube level, all revolving around
a vertical axis and is mounted on a tripod. An Engineer's Level is used
for determining the difference in elevation between two points. The
telescope on the level has a vertical cross hair and a horizontal cross
hair. Once the instrument is leveled, the sighting through the horizontal
cross hair represents a horizontal plane of equal elevation.

Enhanced V
A pattern seen on satellite infrared photographs of thunderstorms, in
which a thunderstorm anvil exhibits a V-shaped region of colder cloud
tops extending downwind from the thunderstorm core. The enhanced V
indicates a very strong updraft, and therefore a higher potential for
severe weather. Enhanced V should not be confused with V notch, which is
a radar signature.

Enhanced Wording

1. An option used by the SPC in tornado and severe thunderstorm watches
when the potential for strong/violent tornadoes, or unusually widespread
damaging straight-line winds, is high. The text that accompanies a watch
of this type will include the line "THIS IS A PARTICULARLY DANGEROUS
SITUATION."

2. Strong wording or emphasis used in a zone forecast issued by a National
Weather Service Forecast Office highlighting a potential condition
(e.g., "some thunderstorms may be severe").

ENHNCD
Enhanced

ENSEMBLE
A collection of numerical model results that show slightly different
possible outcomes.

Ensemble Forecast
Multiple predictions from an ensemble of slightly different initial
conditions and/or various versions of models. The objectives are to
improve the accuracy of the forecast through averaging the various
forecasts, which eliminates non-predictable components, and to provide
reliable information on forecast uncertainties from the diversity amongst
ensemble members. Forecasters use this tool to measure the likelihood of
a forecast.

Ensemble Hydrologic Forecasting
In hydrologic terms, a process whereby a continuous hydrologic model is
successively executed several times for the same forecast period by use
of varied data input scenarios, or a perturbation of a key variable state
for each model run. A common method employed to obtain a varied data input
scenario is to use the historical meteorological record, with the
assumption that several years of observed data covering the time period
beginning on the current date and extending through the forecast period
comprises a reasonable estimate of the possible range of future
conditions.

Ensembles
Reference to a set of computer models run under the concept of Ensemble
Forecasting: multiple predictions from an ensemble of models with
slightly different initial conditions used as input and/or slightly
different versions of models. The objectives are to improve the accuracy
of the forecast through averaging the various forecasts, which eliminates
non-predictable components, and to provide reliable information on
forecast uncertainties from the diversity amongst ensemble members.
Forecasters use this tool to measure the likelihood of a forecast.

ENSO
Abbreviation for El Ni�o-Southern Oscillation, a reference to the state
of the Southern Oscillation.

ENSO Diagnostic Discussion
The CPC issues the ENSO Diagnostic Discussion around the middle of the
month. The discussion addresses the current oceanic and atmospheric
conditions in the Pacific and the seasonal climate outlook for the
following one to three seasons.

ENTR
Entire

Entrainment Zone
A shallow region at the top of a convective boundary layer where fluid
is entrained into the growing boundary layer from the overlying fluid by
the collapse of rising convective plumes or bubbles.

Entrance Region
The region upstream from a wind speed maximum in a jet stream (jet max),
in which air is approaching (entering) the region of maximum winds, and
therefore is accelerating. This acceleration results in a vertical
circulation that creates divergence in the upper-level winds in the
right half of the entrance region (as would be viewed looking along the
direction of flow).

This divergence results in upward motion of air in the right rear quadrant
(or right entrance region) of the jet max. Severe weather potential
sometimes increases in this area as a result. See also exit region, left
exit region.

Entropy
The amount of energy that is not available for work during a certain
process.

Environment Canada
The Canadian federal government department responsible for issuing
weather forecasts and weather warnings in Canada.

Environmental Lapse Rate
The rate of decrease of air temperature with height, usually measured
with a radiosonde.

Environmental Temperature Sounding
An instantaneous or near-instantaneous sounding of temperature as a
function of height. This sounding or vertical profile is usually
obtained by a balloon-borne instrument, but can also be measured using
remote sensing equipment.

EPA
Environmental Protection Agency

EPCTG
Expecting

EPV
Equivalent Potential Vorticity

Equi-Potential Line
In hydrologic terms, a line, in a field of flow, such that the total head
is the same for all points on the line, and therefore the direction of
flow is perpendicular to the line at all points.

Equilibrium Drawdown
In hydrologic terms, the ultimate, constant drawdown for a steady rate of
pumped discharge.

Equilibrium Level
(EL) - On a sounding, the level above the level of free convection (LFC)
at which the temperature of a rising air parcel again equals the
temperature of the environment. The height of the EL is the height at
which thunderstorm updrafts no longer accelerate upward. Thus, to a
close approximation, it represents the height of expected (or ongoing)
thunderstorm tops.

Equilibrium Surface Discharge
In hydrologic terms, the steady rate of surface discharge which results
from a long-continued, steady rate of net rainfall, with discharge rate
equal to net rainfall rate.

Equilibrium Time
In hydrologic terms, the time when flow conditions become substantially
equal to those corresponding to equilibrium discharge or equilibrium
drawdown.

Equinox
The time when the sun crosses the earth's equator, making night and day
of approximately equal length all over the earth and occurring about
March 21 (the spring or vernal equinox) and September 22 (autumnal
equinox). These are reversed in the southern hemisphere.

Equivalent Potential Temperature
The equivalent potential temperature is the temperature a parcel at a
specific pressure level and temperature would have if it were raised to
0 mb, condensing all moisture from the parcel, and then lowered to 1000
mb.

ERLY
Early

ERN
Eastern

Erosion
In hydrologic terms, wearing away of the lands by running water,
glaciers, winds, and waves, can be subdivided into three process:
Corrasion, Corrosion, and Transportation. Weathering, although sometimes
included here, is a distant process which does not imply removal of any
material.



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